JP Patent Kokoku-publication No. 57-14252 discloses such a prior-art apparatus. According to this apparatus, a replacement die is placed on a carriage, the carriage carries the replacement die so that the replacement die is connectable to a clamp claw and flanged rollers mounted on a die plate, and a cylinder means moves the die placed on the carriage to the die plate to engage the die with the clamp claw and the flanged rollers, whereby the die is replaced on the die plate (or pattern plate).
A bottom surface of the die includes a hole into which a piston rod of a working cylinder attached to the carriage and serving to fix the die to the top of the carriage in movement is inserted. Die-plate-side top and bottom surfaces of the die include guide grooves with which the clamp claw and the flanged rollers engage, each groove extending along a travel direction of the die across the top and bottom surfaces of the die.
This prior-art apparatus requires a complicated arrangement including the carriage, the working cylinder and the flanged rollers both attached to the carriage, and a conveyer frame facilitating the carriage to move forward and backward and entails problems in manufacture and manufacturing cost. The die used with the prior-art apparatus requires a severe working accuracy and strength (increasing in wall thickness) because the insertion hole and the guide grooves are defined in the die. Therefore, the number of manufacturing steps increases and then a disadvantage is entailed in cost when a number of corresponding dies are used.
In order to eliminate the problems in such prior-art, a die exchanger of an frameless mold molding apparatus has been developed and disclosed (JP Patent Kokai-publication No. 62-137142).
The apparatus of this publication has achieved a simplification in arrangement and improved the workability and rigidness of the die. However, this apparatus yet requires some improvements.
Namely, the apparatus disclosed in JP Patent Kokai-publication No. 62-137142 is such that the working cylinder 17 of the die carrying-in apparatus 2 can feed only one die at a time, and the die carrying-out apparatus 3 is arranged so that the second support plate 27a, 27b is rotated in order to allow the die to be taken out of the die plate side of the second support plate. Therefore, the arrangement of apparatus is complex, and burdensomes and the number of operation steps is not reduced, yet.